Preparation of unsaturated thio-ethers



Patented Dec. 5, 1950 PREPARATION OF Unsamuasgrap THIO-ETHEBS Ihgmas ,F. Doumani, Los Angelesilalif assignor to 'Union Oil Company geles, Calif., a corporation .of fiailiiornia N ra pplication Au ust .29, 195:5,

Serial No. 613 417 H 11 Claims. n l

This invention relates to the dehydration of dihydric sulfur alcohols to obtain unsaturated thioethers such as (ii-vinyl :tl-iioetherand its homologs. These -.pro d ucts have been found useful as solvents, chemicals, or raw materials for production of resins, rubbers and plastics. This is a continuationrin-part of my copending application Serial No. 446,058, filed June 6, 1942, and now issued as U. S. Patent No. 2,402,878.

The dihydric sulfur alcohols, or as they may also be called, hydroigyalkyl sulfides or hydroxyalkyl thioethers, which are dehydrated by the process of this invention, have the general formula 1 B z RhiQll-ELQQQRz are hydr xysubstituted alkyl or cycloalkyl groups each havthe a l as twp sextet stems. and meter b this pr cesecomp ete dmtien h ve th g neral o ;me a .B Bc which Be at .13 e me e. an swaps ha in cue rmpre deem? s unsat tat nn ea h than do R1 and R2. The process is particularly ap izlicehle t9 these aleQt in R and i al o he em i. 1 se eu yre te It; endthtate uns tura ed, es ecial-1 i he ha e .mere than one d e s unstt1t-rat e se nth tat a e se the .duet vof deh d at on h te a ast We de rees -c l .t ,lntdetetm i the lessees 9f uns tsr to v j :mel u -eiszsq de ee the i es ee of unsa umatien a d-ea h tr. 1e hand is tpns der d as two dea ees Q -en ettut Jen- B1 ana -tim s also-be i te c nnected tn .rin a r ngtit e su t r alte hols which are dehydrated by the prgcess pf this tnv et n. and th p es-nets et the dehyd ati w l beepme alear y e t nse to the ;fQ 1 1ewi-ng exa ples Qf tde adnatien sections incl ded theseope of si, s. mien- Equation 1 Divinylsulfide Equatio Thiodiglycol of'flalifonni-a, IM

Dicyclopentadienyl sulfide H OH Y e l s 2 m f k r 5 DJ;

1, 4 dihydroxy ml iogl ieue thiophane The names shown under the above formulas are the names (of those compounds in which the *Rs represent hydrogen atoms. Also within-the ope of this inte h w er are s mil hydration reactions for the related compounds in which the R15 represent hydrocarbon groups such as :allgyl, cycloalkyl 9r .aryl groups such as methyl, gbutyl, cyclohexyl, methyl cyclopentyl, phenyl, tolyl, benzyl, etc., or the hydroxy substituent groups are attached {to .;Qther carbon .a mst 5 le tious t at to the de d t t eeth the cant n a a ieten to th l ne h ing he bysl txy tuwtmu hav hydrogen attached to it, so that the elimination of water from the moleculeswill form a double bond between these carbon atoms.

An inspection of the abpye equation will show that Equation 1 represents the dehydration of asulfur alic ohollqf tg gnula R1SR2 in which R1 and R2 are hydroxy-substituted saturated alkyl groups; Equation 3 shows the dehydration of a sulfur alcohol in which R1 and R2 are hydroxysubstituted saturated c-ycloallsyl groups; in Equal: tion 3, R1 and Rz'are hydrbxy-substitutd"urisaturated alkyl groups; inEquation 4, R1 and R2 are hydjigoxy-spbsti tyted unsaturated cycloalkyl groups'i-and in Eguation 5, R1 and R2 are interconnectedto form a ring,

It is clear-that th'e aboveequations nierely represent specific'exa-rnples of the dehydration of sulfur alcohols of giiffer ent type'sand the invention is not l'ipiited' etc these specific examples; arhus in Equatiqnd gnplace of {the sulfur alcohol having-tiie-2 hydrexyethyl groups shown,

sulfur alcohols having other saturated hydroxy alkyl groups may be employed. Examples of such saturated hydroxyalkyl groups are 2-hydroxy propyl, 3-hydroxypr0pyl, Z-hydroxy nbutyl, 3-hydroxy isobutyl, 4-hydroxy n-butyl, 2- hydroxy n-amyl, Z-hydroxy iso-amyl, 4-hydroxy iso-amyl, Z-hydroxy hexyl, and like groups in which the R's represent hydrogen or hydrocarbon (alkyl, cycloalkyl or aryl) groups as described above.

Also in place of the sulfur alcohol having the 2-hydroxy cyclohexyl groups in Equation 2, sulfur alcohols having other. saturated hydroxycycloalkyl groups may be employed, such as sulfur alcohols having cyclohexyl groups having the hydroxy substituent in the 3 or 4 position, cyclopentyl groups having the hydroxy substituent in the 2 or 3 position, and hydroxy substituted cyclohexyl or cyclopentyl groups in which one or more hydrogens are replaced by hydrocarbon groups as described above.

Similarly in Equations 3 and 4, in place of the sulfur alcohols having the specific unsaturated groups shown sulfur alcohols having unsaturated groups corresponding to the saturated groups described above for-Equations 1 and 2 may be employed. Also in Equation 5 sulfur alcohols having the hydroxy substituent groups at other positions, or those inwhich the R's represent alkyl, cycloalkyl or aryl groups, or sulfur alcohols having six-membered rings instead of the five-membered rings shown may be dehydrated also. Obviously, in any of the above sulfur alcohols of this invention, the R1 and R2 of the general formula Ri-S-R2 may be the same or different groups.

The above sulfur alcohols which are dehydrated according to a process of this invention may be prepared in a number of ways. Two convenient ways of preparing thiodiglycol, for example, are shown as follows:

Equation 6- H H H H NazS 2C1CCOH (HOC-C-)S +2NaC1 H H H a Ethylene chlorohydrin Thiodiglycol Equation 7 Ethylene oxide Thiodiglycol Sulfur alcohols in which R1 and R2 of the general formula R1- SR2 are different, may be prepared in either of the two ways as follows:

Similar methods may be employed for preparing the other sulfur alcohols which are dehydrated by the process of this invention.

Briefly, therefore, it is theobject of this in-- vention to provide methods of dehydrating the above sulfur alcohols whereby monomeric or Hydroxyvinyl ethynyl sulfide RC=C C=CR Hydroxycyclopentenyl cyclopentadienyl sulfide H OH RC%\ R R i=O l-hydroxydihydrothiophene The invention resides in four types of catalytic dehydration, namely (1) processes involving inorganic acid catalysts, (2) processes involving inorganic salt catalysts (3) processes involving alkali metal hydroxide catalysts, and (4) vapor phase catalytic dehydration processes employing inorganic oxide catalysts. The preferred process is that involving the solid alkali hydroxides as catalysts.

' The action of the-alkali hydroxides as catalysts is unique in that rapid dehydration with essentially no polymerization of the'monomeric olefin products may be obtained. These catalysts are particularly well suited to continuous dehydration processes, since they are not appreciably contaminated by side reaction products. They act as true catalysts in that they do not enter into the reaction, and may be used for a very long time without replacement. These catalysts are also particularly desirable in the reactions involving dehydration of relatively unstable materials which may be destroyed by heat or strong acid catalysts.

In employing these alkali hydroxides in the process of this invention the sulfur alcohols are merely contacted with the solid alkali metal hydroxide at a temperature above C., up to about 300 C., and preferably about 200 C., and the products of the reactionQi. e. the water, and preferably also the unsaturated thioether, are withdrawn as formed. In the preferred liquid phase process, these products are removed by distillation, and the pressure may be adjusted so as to distill these products without distilling the sulfur alcohol. Reflux may be provided to minimize the distillation of the unreacted sulfur alcohol, or some sulfur alcohol distillation may be allowed to take place, and the product redistilled to separate the unreacted sulfur alcohol which may be returned to the system. Where traces of high boilingrproducts air-side reactions are-formed and "accumulate over a long 'period of .time, these usually form a separate-phase insolublein the sulfur alcohol in the presence of thecatalyst, ..and this separate phase may be drawnofi periodically. Potassium hydroxide is the preferred catalyst. ,I-Ioweyer, .sodium hydroxide is also suitable, and the hydroxides of the other alkalimetals,'namelylithium, rubidium and -.caesium may also be employed.

specific examples of the process .of this invention the following experiments were carried out:

. Example 1 2,2 dihydroxyethyl sulfide was prepared by reacting hydrogen sulfide with ethylene oxide as indicated in the above Equation "7. Ten ml. of this product plus g. of solid potassiumhydroxidepellets were heated at 190 to 220 C. 'for about minutes. Water formed in the reactionboiled off during this period and on cooling, the remaining liquid was found to be stratified into two layers. The upper oily layer was removed by decantation, and was distilled to separate two products, namely the product of complete dehydration, divinyl sulfide, and the product of partial dehydration, vinyl hydroxyethyl sulfide. Small amounts of polymeric divinyl sulfide were also found to be present.

In a second experiment employing a continuous process, 10 g. of solid KOH was heated to about 200 C., and 2,2-dihydroxyethyl sulfide was added continuously while the resulting divinyl sulfide was allowed to distill with the water, as formed, through a fractionating column. Substantially complete dehydration of the original sulfur alcohol was accomplished.

In similar experiments 2,2-dihydroxypropyl sulfide (prepared by reacting propylene oxide with hydrogen sulfide) was dehydrated with formation of diallyl sulfide and hydroxypropyl sulfide, the latter having the formula 3,3'-dihydroxypropyl sulfide was similarly dehydrated to obtain diallyl sulfide, employing solid sodium hydroxide pellets in this case and em ploying a temperature between about 00 and 230 C. Similarly, the sulfur alcohol prepared by reacting styrene oxide with hydrogen sulfide,

namely was dehydrated to form distyryl sulfide i 0:0 U s 2 employing solid potassium hydroxide as the catalyst at a temperature of about 220 0.

Example Di(hydroxycyclohexyl) sulfide was prepared by reacting sodium sulfide with chlorocyclohexanol and this sulfur alcohol was dehydrated as in the above Equation 2, by contacting it with solid potassium hydroxide at a temperature of about :80 C- .Q' dQiS H n .off the water has formed. res-substantia :yie d of edicyclo exenyl sulfid well v; as. :the product ofuipartial dehydration :as

shown above was Qobtained atwoihoutso! opera! tion; "In a second experiment. in wbich the-mode uct of complete dehydration, ,dicyclohexenyl sulfide, was distilled oil as :formed, a substantially complete conversion $0 product :was obtained.

In a similar experiment ldiljhydroxyrnethylcyclopentyl) sulfide v as dehydrated in the h e enceet send sod um hyd oxide atraboutzflfi 1 ocbt a p mxie mately 5 e d of the .pmduct Qfcomplete ehydration Sample .3

Bu-tadiene monoxide was :reaeted with hydro.- gen sulfide :to ,obtain the .sul-fur lalcohql having the iqllowihg structure:

r, This -sul-fur alcchc cbntacted w th so id Rolymers of this product were also present.

Up n continuation of 111118 heating further yields of this -=p1:cduc,twerezobtained.

The dehy ation i-shcwn in quation 3, in

which diethynyl sulfide lwaseobtai-ned. was also carried out under approximately the same .con-

ditiq s.

.Emample T e eh rat cn f diihvdwwerclweehny sulfide as illustrated aby Eguation 4 above was carried out in the presence of potassium hydroxide at a temperature of aa ptgoo ,Q, Ibgiling off the water and dicyelqpentadienyl sulfideras formed. A substantial yield was obtained-within an hour. Di"(hydroxycycloh exe1 yl) sulfide was similarly dehydrated, employing solid sodium hydroxide "at -a 'ten peratu re of about 225* 1C.

Jimm e 5 Thetdehydrationpf ll;4edihydroxythiophaneto obtain c-thiophene 483 shown in Equation =5 above was carried out ,as -the above experiments,

ides in solid form may also be employed. These may be supported on inert carriers if desired. The reaction is preferably carried out in the liquid phase as in the above examples, employing a sufiicient pressure to maintain a substantially liquid phase in contact with the catalyst, but the reaction may also be carried out by reducing the pressure sufficiently to maintain the sulfur alcohol in the vapor phase, and contacting these vapors with the solid alkali metal hydroxide. In the vapor phase reaction temperatures somewhat higher than the temperatures employed in the liquid phase reaction, up to about 450 C. are more desirable. v

Although it has been found that heat alone will effect substantial dehydration of sulfur alcohols, which fact is in marked contrast to the behavior of ordinary alcohols, the use of catalysts is preferred. Furthermore, heat and catalysts will polymerize the olefinic products of the dehydration. This permits the combination of dehydration and concurrent polymerization, and even the combination of the three processes, of sulfur alcohol formation, dehydration, and polymerization. In general, temperatures above 150 C. are required for any or all of these reactions (except the alcohol formation itself, which may be carried out at lower temperatures in most instances) and continuous removal of the product water by fractionation is desirable. Suppression of polymerization and acceleration of dehydration is promoted by use of as low a temperature as possible and adjustment of pressure to permit continuous removal, by fractional distillation, of the monomeric product as well as the water. When concurrent polymerization is desired, modifiers such as styrene for example, may be added during the course of the dehydration or polymerization, if co-polymerization or modification of the resinous polymer is desired.

Examples of inorganic acids which are particularly suitable catalysts for the purposes of this invention are sulfuric and phosphoric acids, which should have concentrations above about 90%. These may be used at temperatures of about 150 C. or above, such as about 130 C. to about 200 C. These catalysts are particularly useful when concurrent polymerization is desired.

As an example of the use of inorganic acid catalysts, 10 ml. of thiodiglycol and 1 ml. of concentrated H2804 were heated to about 150 C. for about one-half hour, boiling off water. The product was predominantly the dimer and higher polymers of divinyl sulfide, though some monomer was also present.

Inorganic salt catalysts which may be used include anhydrous or lpartly hydrated zinc chloride (over about 80% concentration), and anhydrous or partly hydrated ferric chloride or tin chloride. In general, these induce dehydration at slightly lower temperatures than those required for the alkali metal hydroxide catalysts. They are more similar in this respect to the inorganic acid catalysts, and also promote substantial polymerization of olefinic products. Again continuous removal of the monomer represses polymerization. As an example, 10 ml. of thiodiglycol was heated with 10 g. of anhydrous zinc chloride to a temperature of about 200 C. for about one-half hour, allowing water and monomeric divinyl sulfide to distill olf. Considerable polymeric product was found in the residue.

Vapor phase dehydration, using inorganic oxide catalysts such as activated alumina-bauxite, clay, fullers earth, and silica gel, is effective especially at temperatures above 200 C., and is accompanied by considerable polymerization. The degree of polymerization may be controlled to a considerable extent by regulation of the temperature and pressure and by use of inert gases as diluents or carriers, in general low temperatures, low pressures and diluents having the effects of depressing polymerization.

As an example of this process, 50 ml. of granular activated alumina was placed in a tube heated to 325 C. and thiodiglycol vapors were passed over the catalyst, using a feed rate of 50 ml. per hour. The product, when condensed, was found to be largely divinyl sulfide and its polymers.

Similar results were obtained with sulfur alcohols of this invention other than thiodiglycol, using the acid, salt, and oxide catalysts as described above.

Although the above description of the invention has been confined to the dehydration of dihydric sulfur alcohols, it has been found that substantially the same procedure may be employed for the dehydration of monohydric sulfur alcohols. The dehydration reactions for the monohydric sulfur alcohols corresponding to the dehydration reactions for the dehydric sulfur alcohols shown in Equations 1 to 5 above are indicated in Equations 1A to 5A as follows:

Ethyl hydroxyethyl sulfide Ethyl vinyl sulfide C--C B.

Methyl cyclohexenyl sulfide Equation 3A RCR Isopropyl 2-hydroxy,

Isopropyl butadienyl sulfide 3-butenyl sulfide As examples of these dehydrations, 10 ml. of ethyl-hydroxyethyl sulfide (prepared by reacting ethyl mercaptan with ethylene oxide) and lo a.

'ze ssap'm of solid potassium 'hydroxide pellets were heated .at2l90" C. :to 12201C..for twenty minutes. Water formed in the reaction boiled off .during this period, and the -zremainingiliguid "stratified' into layer, and re-heated to the original temperature of about 200 C. for another 20 minutes, at which time it was found that as nearly as could be observed, all of the original alcohol had been converted to monomeric ethyl viny1 sulfide.

In another mode of carrying out this reaction an arrangement of apparatus was made whereby g. of solid KOH was heated to about 200 0., while ethyl hydroxyethyl sulfide was added at a rate of about 1 ml./min., and water and monomeric ethyl vinyl sulfide were removed continuously through a fractionating column. After about an hour an equilibrium was established at which the rate of production was approximately equal to the rate of feed. No appreciable deterioration of the catalyst was observed in several hours of operation.

In similar experiments butyl hydroxyethyl sulfide was dehydrated at a temperature of about 225 C.; the sulfur alcohol prepared by reacting thiophenol with styrene oxide, was dehydrated at a temperature of about 250 C. in the presence of solid sodium hydroxide to obtain substantial yields of phenyl styryl the sulfur alcohol s-o con H H prepared by reacting thiophenol with ethylene oxide, was also dehydrated under the above conditions to obtain phenyl vinyl sulfide; and the dehydrations indicated in Equations 2A to 5A were carried out with the specific materials named as well as with homologs thereof. In all of these dehydrations the conditions described above for the dehydration of the dihydric sulfur alcohols were found to be suitable also for the dehydration of the monohydric sulfur alcohols.

It is within the scope of this invention therefore to prepare an unsaturated thioether by contacting the corresponding hydroxy-substituted thioether (including both the monohydric and dihydric sulfur alcohols described above) with a catalyst maintained at a temperature above about 150 0., the preferred catalysts being the solid alkali metal hydroxides, using a reaction time sufficient to split out water from the molecule and thereby form the desired unsaturated thioether, and removing the water and preferably also the unsaturated thioethers, as formed.

Modifications of this invention which would occur to one skilled in the art are to be included in the scope of the invention as defined in the following claims.

I claim:

1. A process for the preparation of an unsaturated thioether which comprises contacting a dihydroxy-substituted thioether having the formula R1SR2 in which R1 and R2 are hydroxy- 10 substituted hydrocarbon groups 'having at least two :carbonr atoms wi-thra solid alkali imetal hydroxide maintained at a temperature abovlel=1=5ll 0., for ai-timelsufficient .to=spli-tout at least one molecule of water from the molecule and form an=unsaturated thioether, and continuously re- 'moving sai'd water asformed.

process according -to claim 1 in which the alkali metal hydroxide is potassium hydroxide.

'3."la'process according'to claim 1 in "which 'tlre alkali"m'etal hydroxide is sodium hydroxide.

4. A process for the preparation of an unsaturated thioether which comprises contacting a saturated dihydroxy-substituted thioether having the formula R1-S-Rz in which R1 and R2 are I hydroxy-substituted saturated hydrocarbon groups having at least two carbon atoms with a solid alkali metal hydroxide maintained at a temperature above C. for a time suflicient to split out at least one molecule of water from the molecule and from said unsaturated thioether, and continuously removing said water as formed.

5. A process according to claim 4 in which the saturated dihydroxy-substituted thioether is a di(hydroxyalkyl) thioether.

6. A-process according to claim 4 in which the saturated dihydroxy-substituted thioether is a di(hydroxycycloalkyl) thioether.

7. A process for the preparation of an unsaturated thioether which comprises subiecting a saturated dihydroxy-substituted thioether having the formula R1-S-R2 in which R1 and R2 are hydroxy-substituted saturated hydrocarbon groups having at least two carbon atoms to a temperature above 150 C. in the presence of an inorganic dehydration catalyst for a time sufllcient to split out at least one molecule of water from the molecule and form said unsaturated thioether, and continuously removing said water and unsaturated thioether as formed.

8. A process for the preparation of an unsaturated thioether which comprises contacting a saturated dihydroxy-substituted thioether having the formula R1SR2 in which R1 and R2 are hydroxy-substituted saturated hydrocarbon groups having at least two carbon atoms with a solid alkali metal hydroxide maintained at a temperature above 150 C. for a time suflicient to split out at least one molecule of water from the molecule and from said unsaturated thioether, and continuously removing said water and unsaturated thioether as formed.

9. A process according to claim 8 in which the alkali metal hydroxide is potassium hydroxide.

10 A process for the preparation of a vinyl alkenyl thioether which comprises contacting a hydroxyethyl, hydroxyalkyl thioether with a solid alkali; metal hydroxide maintained at a temperature above 150 C. for a time sufficient to split out water from the molecule and form said vinyl alkenyl thioether, and continuously removing said water and vinyl alkenyl thioether as formed.

11. A process for the preparation of divinyl sulfide which comprises contacting 2,2'-dihydroxyethyl sulfide in the liquid phase with solid potassium hydroxide at a temperature above about 150 C. for a time sufficient to split out water from the molecule and form divinyl sulfide; while continuously distilling off said water and divinyl sulfide as formed.

THOMAS F. DOUMANI.

(References on following page) 11 12 7 REFERENCES CITED -OTHER"REFERENCES The following references are of record in the Clayton et a1.: Jour. Am. Chem. S0c., v01. 64, file of this patent: pages 908909 (April 1942). UNITED STATES PATENTS Fromm: Berlchte Deut. Chem. (365611.,H V01. 5 56, pages 22862289 (1923). Number N Date Bales et 51.: J. c. s. (London), vol. 123, page 2,221,418 We1he NOV. 12, 1940 243 1923 r; 3 1 0km June 19,1945 Sabatay: Bull. Soc. Chim. (Ser. 4), vol. 45,

' FOREIGN PATENTS 10 pages 69 to 75 (1929). 3 Number Country Date 485,554 Great Britain May 16; 1938 

1. A PROCESS FOR THE PREPARATION OF AN UNSATURATED THIOETHERE WHICH COMPRISES CONTACTING A DIHYDROXY-SUBSTITUTED THIOETHER HAVING THE FORMULA R1-S-R2 IN WHICH R1 AND R2 ARE HYDROXYSUBSTITED HYDROCARBON GROUPS HAVING AT LEAST TWO CARBON ATOMS WITH A SOLID ALKALI METAL HYDROXIDE MAINTAINED AT A TEMPERATURE ABOVE 150* C., FOR A TIME SUFFICIENT TO SPLIT OUT AT LEAST ONE MOLECULE OF WATER FROM THE MOLECULE AND FORM AN UNSATURATED THIOETHER, AND CONTINOUSLY REMOVING SAID WATER AS FORMED. 